Patent Grant
8772356
This invention relates to a composition for treating inorganic slurries and to a method of treating inorganic slurries with the aforesaid composition so as to maintain the slurries in a substantially homogeneous phase.
The present invention will be described herein with particular reference to calcium carbonate-based slurries, especially those used in paper-making processes, although it is not to be construed as being limited thereto.
Most inorganic slurries contain about 70% to 80% by weight of solids. Many inorganic slurries (particularly those based on calcium carbonate) are known to be susceptible to bacterial contamination and it has been the practice to add one or more biocidally-active materials to the slurries in order to minimise such contamination.
Phosphorus-containing compounds, in particular tetrakis(hydroxyorgano)phosphonium salts (THP+ salts) are known to be effective biocides. Experimental work carried out by the applicants has shown, for example, that the addition of a solution of tetrakis(hydroxymethyl)phosphonium sulphate (THPS) to a calcium carbonate-based slurry can give rise to a reduction in bacterial count of 104 in 2 hours.
However, it is also known that addition of THPS alone to a slurry results in instantaneous heterogeneous thickening and aggregation of the slurry.
The applicants have found that the use of a composition comprising a THP+ salt and a dispersant will provide continuing preservation against bacterial contamination, while at the same time maintaining the slurry in a substantially homogeneous phase.
Accordingly, in a first aspect, the present invention provides a composition for treating an inorganic slurry, the composition comprising:
(a) a tetrakis(hydroxyorgano)phosphonium salt (hereinafter THP+ salt); and
(b) a dispersant selected from the group consisting of:
and (iv) polyphosphates.
In accordance with the present invention, the THP+ salt is preferably tetrakis(hydroxymethyl)phosphonium sulphate.
Alternatively, the THP+ salt may be tetrakis(hydroxymethyl)phosphonium chloride, phosphate, nitrate or oxalate.
A preferred example of a dispersant of the type (b)(i) is a compound having one tertiary nitrogen atom, such as a sodium salt of nitrilotris(methylene phosphate), particularly the tetra-sodium salt.
Preferred examples of dispersants of the type (b)(ii) include those oligomers having the general H(CH2OM.CH2OM)nPO3M2, wherein M is a cationic species such that the oligomer is soluble in water and n is a number greater than 1.
Other suitable oligomers are disclosed in the applicant's European Patent Specification 0 491 391.
A preferred example of a dispersant of the type (b)(iii) is a homopolymer of acrylic acid, especially a homopolymer having a molecular weight in the range 2000 to 5000.
Preferred examples of dispersants of the type b(iv) include sodium tripolyphosphate.
In a second aspect, the present invention provides a method of treating an inorganic slurry to maintain the slurry in a substantially homogeneous phase, the method comprising the addition to the slurry of an effective amount of a composition according to the first aspect of the present invention.
The inorganic slurry may, for example, comprise a calcium carbonate-based slurry.
Alternatively, the inorganic slurry may comprise a pigment slurry, a clay slurry or a cement slurry.
Preferably, the ratio of THP+ salt to dispersant in the composition is about 2:1 (as active ingredients).
Suitably, the composition may be added to the slurry in an amount in the range 10 ppm to 1000 ppm (by weight of the slurry), for example about 750 ppm (by weight of the slurry).
The present invention will be illustrated by way of the following examples.
In the examples, a 75% calcium carbonate slurry (commercially known as Setacarb) was treated with:
THP+ salt alone.
THP+ salt and dispersant of type (b)(i).
THP+ salt and dispersant of type (b)(ii).
The amounts of each additive used, and the results, are given in the TABLE below.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0301975.9 | Jan 2003 | GB | national |
This application is a continuation application of application Ser. No. 13/586,012 filed Aug. 15, 2012 (abandoned), which is a continuation application of application Ser. No. 10/542,432 filed Nov. 16, 2005 (abandoned), which is a United States national phase application of International application PCT/GB 2004/000056 filed Jan. 12, 2004. The entire contents of each of Ser. Nos. 13/586,012 and 10/542,432 and International application PCT/GB 2004/000056 are hereby incorporated by reference herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2877848 | Case | Mar 1959 | A |
| 3336221 | Raulston | Aug 1967 | A |
| 3597251 | Kaufman | Aug 1971 | A |
| 3832302 | Lansford et al. | Aug 1974 | A |
| 3945843 | Holty et al. | Mar 1976 | A |
| 4673509 | Davis et al. | Jun 1987 | A |
| 4874526 | Grade et al. | Oct 1989 | A |
| 5386038 | Davis et al. | Jan 1995 | A |
| 5606105 | Davis et al. | Feb 1997 | A |
| 5741757 | Cooper et al. | Apr 1998 | A |
| 6180056 | Comstock et al. | Jan 2001 | B1 |
| 6315867 | Skuse et al. | Nov 2001 | B1 |
| 6402824 | Freeman et al. | Jun 2002 | B1 |
| 20020144797 | Skuse et al. | Oct 2002 | A1 |
| 20030226808 | Fidoe et al. | Dec 2003 | A1 |
| Number | Date | Country |
|---|---|---|
| 0 491 391 | Jun 1992 | EP |
| 0 839 956 | May 1998 | EP |
| 1 160 201 | Dec 2001 | EP |
| 2 379 440 | Mar 2003 | GB |
| WO 9614092 | May 1996 | WO |
| WO 9933345 | Jul 1999 | WO |
| WO 0004777 | Feb 2000 | WO |
| WO 0208127 | Jan 2002 | WO |
| Entry |
|---|
| “slurry.” Merriam-Webster Online Dictionary. 2009. Merriam-Webster Online. Jul. 2, 2009. <http://www.merriam-webster.com/dictionary/slurry>. |
| Number | Date | Country | |
|---|---|---|---|
| 20130225534 A1 | Aug 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13586012 | Aug 2012 | US |
| Child | 13856058 | US | |
| Parent | 10542432 | US | |
| Child | 13586012 | US |
